Algebra

[earnest salmon]

$(\dfrac{1}{a}-1)(\dfrac{1}{b}-1)(\dfrac{1}{c}-1) \geqslant 8$

[upper spade]

Orbion

[earnest salmon]

~~what I would do is :

• multiply everything by abc
• replace c using a+b+c=1
• find an inequation in a (or in b)
• solve it~~